FR2530617A1 - METHOD FOR FIXING A FIBER-REINFORCED GLASS MATRIX COMPOSITE MATERIAL TO STRUCTURAL ELEMENTS - Google Patents

Abstract

THE PRESENT INVENTION CONCERNS A PROCESS FOR FIXING A COMPOSITE MATERIAL WITH A FIBER REINFORCED GLASS MATRIX TO STRUCTURAL ELEMENTS. A RIVET OR BOLT PREFERRED ATTACHMENT MAY BE ACHIEVED BY HOT PRESSING A GLASS MATRIX MATERIAL IN AND AROUND CONTINUOUS LENGTH SILICON CARBIDE FIBERS ORIENTED IN A SINGLE DIRECTION. SUCH A MATERIAL IS WORKED ON AND POSSIBLY PROVIDED WITH THREADS. AFTER REALIZATION, THE BOLT OR THE RIVET ARE INSERTED IN AN OPENING PROVIDED FOR FIXING THE MATERIALS TOGETHER AND THE FREE END OF THE RIVET OR BOLT IS CLOSED EITHER BY MEANS OF A NUT OR BY HOT DEFORMATION. THE INVENTION CAN FOR EXAMPLE BE USED FOR ATTACHING GAS TURBINE ELEMENTS.

Description

The present invention relates to a method for fixing a composite material

  fiber reinforced glass matrix to structural elements, in particular by mechanical means. Because of the increasing scarcity and cost of many structural metals that can be used at high temperatures, increased attention has been given to

  non-metallic fiber-reinforced composites to replace

  The use of high strength fiber reinforced resin and even matrix composite materials

  metal reinforced with high strength fibers in

  Placement of metals has progressed to a point where they are commercially acceptable for articles from sporting goods to engine parts.

  One of the big problems with these struc-

  Composite tures however was their maximum temperatures of use.

  Bodies of ceramic material, glass and glass

  are known in the art which can be

  used in high temperature applications.

  Unfortunately, however, these bodies often have

  insufficient mechanical resistance and are invariable

  deficiencies in toughness and resistance

  This situation has given rise to the preparation of composite bodies consisting of a matrix of ceramic material, glass or glass-ceramic with inorganic fibers dispersed continuously or discontinuously therein. glass

  are described in US Pat. Nos. 4,314,852 and 4,324,443.

  As noted above, possible applications of these materials are anticipated in the gas turbine engine industry and other areas of high temperature engines where the superior fracture toughness The oxidation and low density of these materials will result in a marked improvement in overall engine efficiency and fuel consumption. Similarly, it is anticipated that these fiber reinforced composites will be preferred in many non-engineered structures. motor but used at high temperatures because of their excellent toughness and resistance to oxidation by comptration to composite structures of ceramic materials and carbon-carbon However problems have been

  encountered and are intended to fix these composi-

  to these or other structural elements such as elements of metal or ceramic material in these environments These fasteners must remain sealed over large temperature ranges and must not cause corrosion of the fasteners because of the interaction of the material or the interaction of the elements with the motor medium In most cases, it is intended that the fiber-reinforced composite material

  and its attachment will be exposed to extreme temperatures.

  Consequently, such fastening means will have to undergo

the severe conditions of the environment.

  Accordingly, what is necessary in the art is a method of fixing the matrix composite materials

  fiber-reinforced glass to other structural elements

  in a safe manner for prolonged periods of time.

  and in extreme environmental conditions.

  According to the present invention a process is described

  for fixing a glass matrix composite material

  forced to a structural member A rivet or bolt of silicon carbide fibers of continuous length or

  discontinuous in a stable glass matrix at high temperature

  is produced by molding or hot pressing and is then used to fix the composite material to

  the structural element The use of such a means of

  This results in a combination of composite structural material which remain tight together under difficult conditions such as extreme temperature conditions. The structural element may be a fiber reinforced glass matrix composite material itself or another structural material such as another composite material, a non-reinforced ceramic material

or a metal.

  Another object of the invention is a method of manufacturing

-3-

  such rivets or bolts consisting of forming a sheet of

  fiber composite material reinforced with orien-

  uni-directionally continuous length tees, cut rectangular sections of this sheet, calibrate these rectangular sections into cylindrical shapes and form bolt heads on these forms thus treated According to a preferred embodiment, the rivet or bolt of the sheet of material Composite is obtained by hot pressing a glass matrix mixture containing about 20% to about 60% by volume of high temperature stable fibers In the case of a bolt, threads are also machined or calibrated

  by striking on the cylindrical form.

  So that the invention can be better understood, reference is made to the drawings o:

  FIG. 1 represents preforms, molds or

  Typically calibrated templates useful for practicing the present invention; Figure 2 shows a typical mold for forming the rivet head according to the present invention; Figure 3 shows rivets produced according to the present intentin; Figure 4 is a photomicrograph of a section of such a rivet; Figure 5 shows a voltage-elongation diagram for the rivets during the tests; Figure 6 shows rivets broken after the tests;

  FIG. 7 shows a threaded bolt according to

  FIG. 8 represents the load required to shear the threads of composite glass-ceramic material plates.

  reinforced silicon carbide usable according to the present inventk: n.

  Both the materials and methods of preparation of the fastening means according to the present invention are as described in US Pat. Nos. 4,314,852 and 4,324,843. As described, although any borosilicate glass which will impart high temperature resistance to the composite material according to the present invention can be used, it has been found that

  Corning 7740 (Corning Glass Works) was suitable for this process.

  Similarly, Corning 7930 (about 96% by weight silicon) obtained by leaching boron out of borosilicate glass, and Corning 1723 are high-grade glasses.

  preferred silica and aluminosilicate content

  Although borosilicate glass and aluminosilicate glass can be used as received with particles having a size of the order of 0.044 mm, the desired properties for high silica glass composite materials can only be satisfactorily manufactured with the glass after it has been milled

  ball in propanol for more than 100 hours.

  It should also be noted that blends of the above glasses may also be used although any glass or glass ceramic that will impart the required strength and stability to the composite materials of the present invention can be used.

  used, it has been found that the composite material of

  lithium aluminosilicate porcelain was suitable

particularly well for this purpose.

  During the densification of the composite structure, this matrix is kept in a vitreous state, avoiding

  thus damaging the fibers and promoting the densi-

  After densification into the desired matrix plus fiber form, the vitreous matrix can be converted to a crystalline state, the degree of crystallization of which is controlled by the composition of the matrix and the heat treatment program used. A wide variety of glass-ceramics can be used in this manner. However, when using silicon carbide fibers, a strict limitation of the amount and activity of the titanium present in the glass is of paramount importance. silicon carbide fibers and titania agents are used, the titanium oxide must be inactive or maintained below 1% by weight This can be achieved by simply using another germinating agent such as than zirconium oxide instead of the usual titanium oxide or by adding an agent to mask the reactivity of the titanium oxide towards the However, in

  all cases it is necessary to either eliminate or

  the effects of titanium oxide on silicon carbide fibers to achieve a composite structure

  having good mechanical strength properties at temperatures

  Although the usual lithium aluminosilicate is the preferred glass-ceramic material, other

  conventional glass-ceramic materials such as aluminum

  silicate, magnesium aluminosilicate and combinations thereof can be used as long as the ceramic matrix material does not contain titanium (less

  about 1% by weight) or masked See US Pat.

  4,324,843 In general, the starting material of vitroceram

  can be obtained in the vitreous state in powder form.

  If, however, the ceramic material is obtained in crystalline form, it will be necessary to melt it to form a vitreous state, to solidify it and then to grind it into a powder, preferably with grains of 0.044 mm, before making the pasta according to present invention He is

  important in choosing the glass-ceramic material from

  one that can be densified in the vitreous state with a sufficiently low viscosity to allow densification

  complete with subsequent transformation into a sensi-

  It is also possible, however, to convert the starting crystalline powder into a vitreous state during the heat pre-treatment.

  before the application of pressure for densification.

  While any high temperature stable fiber material may be used in the process according to the present invention, silicon carbide fibers are particularly preferred. A silicon carbide multifilament yarn with an average filament diameter of up to 50 μm, Example 5 at 50 μm, is particularly preferred Nippon Carbone Company of Japan produces such a yarn with about 250 fibers per rope and a mean fiber diameter of about 10 μm. The average fiber strength is about 2000 Pa.m. at a temperature of use up to 12000 C The rope has a density of about 2.6 g / cm 2 and a modulus of elasticity of about 221 6- G Pa. If the fixation is carried out with the mode of embodiment of the rivet according to the present invention, the end of the rivet is sealed as an ordinary rivet by increasing its temperature beyond the point of softening of the glass matrix to prevent it from going out by sliding If a bolt-on embodiment is used, a usual metal nut or a nut of glass-fiber or glass-fiber composite material made by cutting

  such pieces from a rectangular sheet of

  As described above for the rivet, or by the injection molding process, it can be used. The parts to be fastened together are drilled with holes to fit the rivets and bolts according to the invention.

present invention.

  The drilling of the vitroceram matrix composite material is best carried out using a diamond core drill. Alternatively, suitably arranged holes may be formed when the parts concerned are formed, for example by molding. of articles which can be fastened together according to the present invention are gas turbine engine elements such as the external tire, the combustion chamber wall segments, the conduits to the afterburner chamber, spraying and vanes, these elements being made of composite material with a glass matrix or other composite materials which are stable at high temperature or in a material

  unreinforced ceramic stable at high temperature.

Example 1

  A composite composite board was fabricated

  this lithium ferride aluminosilicate reinforced with silicon carbide fibers oriented in a single direction of 7.6 cm × 7.6 cm × 0.345 cm), as described in US Pat. No. 4,324,843. This composite plate was cut out in stems approximately 0.53 cm wide This gives a cross-sectional area of the stem roughly equivalent to that of a round rod 0.48 cm in diameter These rectangular rods

  serve as a preform A mold of round rods is made

  tightening together two 7.6 cm x 7.6 cm x 1.3 cm graphite plates separated by a 0.015 cm thick board and drilling holes symmetrically around the center of the plate using a drill ( No. 10) 0.49 cm in diameter 0.0076 cm thick molybdenum sheets were deformed to fit the shape of the thus-formed graphite mold. The rectangular rods were arranged in a manner suitable between the molybdenum separators and the the assembly was placed in a hot machine and heated up to 14000 C

  under the argon atmosphere When this temperature has been reached

  The preforms are shown in FIG. 1A, the molds in FIG. 1B and the rods calibrated by striking in FIG. 1C.

  A second key calibration operation was used

  The mold for this operation is shown in FIG. 2 and consists of a graphite block (21) with holes (22) drilled into the rivets.

  this one to fit the rivets and the co-section

  The press plate (24) is also shown to form the finished rivets shown in FIG. 3. A microphotographic representation of the composite structure of an axial section through the head of one of the rivets is shown. in Figure 4 These rivets were tested under tension The heads were held by means of a milled bearing and the rod by means of soft metal sleeves caught in a clamp has two jaws and tensioned at a rate

  0.127 cm per minute until rupture occurs

  duise All cracks were occurring at the base of the

  head (51) as shown in FIG.

  were gradual rather than abrupt and the samples

  lons sustained high loads even after training

  the first crack as shown in

  voltage-elongation diagram of FIG.

-8-

Example 2-

  It has been determined that stems of composite material

  Silicon carbide-reinforced glass-ceramic matrix could be threaded as shown in Figure 7 by single-point cutting at the turn. Threading can also be achieved by calibrating the same-way

  and at the same time that the first rod form is made.

  Although the tests were not carried out to determine

  To eliminate the breakage of the threads made, the values of the loads supported by threaded plates of composite material of glass matrix reinforced with fibers oriented at angles 00/900 are representative of the load necessary to use, by shear, the threads, this material. and this is shown in FIG. 8. It can be seen that the fillers until thread breakage is suitable for a material having a resistance to

shear of about 44.7 M Pa.

  Although multiple calibration techniques have been used to produce materials for fixation, it can be understood that such methods can be automated for mass production and for the most part.

  a large part of the applications

  brage would suffice to form the fixing device.

  Naturally various modifications may be made by those skilled in the art to the processes which have just been described solely as non-limiting examples.

  without departing from the scope of the invention.

_ 9 _

Claims (6)

claims:   1 Method for fixing a fiber reinforced glass matrix composite material to a structural element characterized in that it consists in molding and machining: a fiber-reinforced glass matrix composite material stable at high temperature in a rivet or bolt forming substantially concentric holes in the composite material and the structural member at their point of attachment, securing the composite material to the structural member by inserting the rivet or bolt through the holes and closing the open end of the rivet or bolt deformed by heat or by means of a nut respectively, so as to produce a composite material-structural element structure which remains tight   under extreme temperature fluctuations.   Process according to claim 1, characterized in that the structural element is a glass matrix material   reinforced with silicon carbide fibers.   Process according to Claim 1, characterized in that the structural element is a metal. Process according to Claim 1, characterized in that the structural element is a ceramic material,   glass or unreinforced glass ceramics.   Process according to Claim 1, characterized in that the high-temperature stable fibers are of silicon carbide, graphite or alumina. 6 Process for manufacturing a rivet or bolt made of fiber-reinforced glass matrix composite material   characterized in that it consists in hot pressing a mixture   of glass matrix containing about 20% to about% by volume of stable fibers at high temperature to form a sheet of composite material reinforced with high temperature stable fibers, cutting the sheet into substantially square cross-section stems, heating the cut stems in a mold for deforming these rods into stems of substantially circular cross-section heating one end of the deformed rods to form a flat head section 7 Method according to claim 6, characterized in that it consists in calibrating by striking the threads on the stems during or after formation of the section   substantially circular transverse.   8 Process according to claim 6, characterized in that it consists in calibrating by striking threads   on the rods of the cylindrical cross section.   Process according to Claim 6, characterized in that the reinforcing fibers are carbide silicon graphite or alumina.   Method according to claim 6, characterized in that   that the material of the matrix is in borosilicate, alumnno-   silicate, glass with a high silica content or vitroceram of lithium aluminosilicate.